Electron discharge device of the magnetron type



YPE

Feb. 12, 1952 w. c. BROWN ELECTRON DISCHARGE DEVICE OF THE MAGNETRON T Filed Oct. 16, 1945 Patented Feb. 12, 1952 ELECTRONDISGHARGE' DEVICE OF THE MAGNETRON TYPE William C. Brown; Watertown, Mass assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware ApplicationOctober 16, 1943, SerialNo. 506,608

Claims. 1 This invention relates to an oscillator for the generation of ultra-high frequency oscillations having wave lengths of the order or'afew centimeters of less.

In devices of this kind it is desirable that the oscillations generated be fed into a transmission system, such as a hollow wave guide, in a. direct and efficientmanner; Particularly in high-power oscillators; the. problem of coupling the-oscillating elements to the transmitting system becomes acute: It is therefore an object of this-invention to' feedthe' energy of the oscillating portion of an ultra-high. frequency generatordirectly into a-transmission system inanefiectiveand efficient manner.

Where a magnetron of the multiple anode type is used as a. generator in systemsct the above kind, a tendency has heretoforev existed for the oscillator to operate. not only at the dc? sired irequency but alsoatvarious spurious. frequencies which decrease the efficiency and effectivenessof the device.

Another. object of this invention is to eliminate such-tendencies to generate spurious oscillations,

whereby substantially. all of the oscillating energy is concentrated inthe desired wave length.

The'foregoing and other objects of this invention will be best understood from the following description of an exemplification thereof, reference being had to the accompanying drawings, wherein:

Fig. 1 is a perspective view partly broken away ofan arrangement builtin accordance with my invention;

Fig. 21s a vertical .cross sectiono'f the arrangement'shown'in Fig. 1 mounted between a pair of magnet poles; and

Fig. 3-'is. a horizontal cross-section taken ap=- proximately along line 3-3 of Fig. .2.

Thedrawings' illustrate a: magnetron of: the multiple-anode type in which the anode structure l consists of a block. of highly-conductive metal, such ascopper Said block isformed with a-central opening 2. A pluralityof radial-slots 3- are' formed in the-resultingannular structure. Said slots extend longitudinally from one flat surface of the copper block-v to within a short distance-of the other flat surface thereof. This leaves a solid end ring 3a whichserves tosupport resulting wedge-shaped anode sections. v A cathode is supported within the central opening 2 to cooperate with the plurality. ofwedge-shaped anode sections. The cathode 4 is of" the indirectly-heated thermionic type having. an outer conducting sleeve coated with emissive material anda central heater. 5' from which leads Band 7 extend at opposite ends of the cathode structure. One of saidleads, for example. i, is-likewise electrically connected to the conducting sleeve ofsaid cathode. Preferably shields 8-8 are supported .on leads 6 and 'i at opposite ends of the. cathode structure so as to intercept any electron beams which otherwise might tend to be projected outwardly from the cathode toward the ends. of the tube structure.

The structure. above described isprovided with a pair of end rings. 9, 9.1n the outer ends of which are placed closure'capsl 0-40. The anode structure, together with'the end rings and closure caps; are'soldered together; preferably. by silver "solder; in order'toiorm an hermetically-sealed structure which can'be evacuated in accordance with the usual high vacuum technique.

Thecathode structure is supported by a' pair of cathode lead-in conductors H connected re.- spectively to the'leads 6 and I. The lead-in conductors H extend through pipes l2 which carry glass seals l3 at the outer ends thereof. The conductors H likewise extend through said glass seals. The pipes I2 are hermetically sealed in openings in the rings 9;

The cavities formed by the radial slots 3 each constitutesa resonantfpassage'. Thus when the tube is placedbetweensuitable magnetic poles l4" and is energized with the proper voltages, oscillatory currents areset up in the resonant passages formed'by' the radial slots-3L In order to feed these oscillations into an output device, the tube is provided with an external resonant cavity member- [5 consisting of a hollow annulus which is open along its inner side. Extending from the upper and lower sides of this opening are rings it which overlap the ends of the anode structure I, and may extend under the inner ends'of the rings 9. It is, of'course, to 'be'understood that in such an arrangement the resonant cavity member I5 is assembled with the other elements ofthe tube structure and soldered'into place in order' to form an hermetic seal.

The cavity member l5together with the outer surface of the anode structure I form a complete oscillator cavity resonator. I have found that such a cavity. resonator can be excited into its oscillatory condition by feeding oscillatory energyj into' said resonatorthrough a slot along itsinside wall which is hereformed by the outside surface ofthe. anodestructure L. I have also found that such oscillatoryv energy can be fed" into the cavity'reson'ator through a pluralityj ofislots which are located. at predetermined points spaced from each other along said inner wall of the cavity at the proper intervals. The radial slots 3 can likewise be caused to perform such an exciting function so that the energy generated by the oscillations produced within the anode structure I is passed directly into the cavity resonator I5. Since, as I have pointed out above, it may be desirable to excite the cavity resonator I5 only at points spaced 2. predetermined distance apart, and since the outer ends of all of the slots 3 may not be thus properly spaced, I may cause selected slots 3 to serve as exciters for the cavity resonator. This is done by placing plugs I! in the outer ends of those slots from which it is desired to prevent energy from being fed directly into the cavity resonator I5. While these plugs may be separate conducting members inserted into the slots. they may likewise be formed integrally with the anode structure. In the arrangement shown I have illustrated a magnetron having twelve radial slots or resonant passages, and in which every fourth slot is caused to act as an exciter for the cavity resonator I5. In such an arrangement the active slots will bear the proper phase rela tionship with respect to said cavity resonator so that all of said slots feed energy into said cavity resonator.

In order that a maximum efficiency of energy transfer from the oscillating slots into the cavity resonator shall occur, the following relationships should preferably exist. The total length of each slot 3 from the central opening 2 to the outer wall of they anode structure I should be about half a wave length of the desired oscillations. The length of each plug I'I should be a quarter of such a wave length. The rings I6 should likewise overlap the ends of the anode structure I to substantially the same extent as the length of the plugs I1, namely a distance equal to about one-quarter of said wave length. Under these conditions the points at which the cavity resonator I5 comes into contact with the anode structure I are high impedance points, and thus the impedance of any load which is energized from the cavity resonator I5 is reflected with maximum efiectiveness into the oscillating slots of the magnetron structure.

The oscillations which are fed into the cavity resonator I5 may likewise be fed from said cavity resonator directly into a transmission system, such as a hollow wave guide. For this purpose the cavity resonator I5 may be supplied at one portion thereof with a longitudinally extending slot I8. A conducting pipe I9 forming a portion of a hollow wave guide is connected to the outer wall of the cavity resonator I5 around said slot I8. The pipe I9 may likewise be soldered into place on the cavity resonator I5 so as to form an hermetic seal therewith. The outer end of the pipe I9 may be hermetically sealed by a glass plate 20 fused thereon. The pipe I9 is coupled with a pipe 2|, constituting an output hollow wave guide, through a suitable choke coupler 22.

I Such an arrangement as I have described above not only feeds the energy of the oscillating slots 3 into the cavity resonator I5 at a plurality of points in a direct and efiicient manner, but also possesses a number of additional advantages. The cavity resonator I5 is intimately and directly coupled to all'of the slots 3 within the magnetron structure, so that said cavity resonator tends to lock in the frequency at which each of said slots oscillates with the frequency of oscillations flowing within the cavity resonator. This effect is so strong that substantially no tendency exits in the structure for any spurious oscillations to be generated.

Of course it is to be understood that this invention is not limited to the particular details as described above as many equivalents will suggest themselves to those skilled in the art. For example, other types of tube structures as well as various types of cavity resonators may be utilized, and also various other types of output transmission systems, including concentric transmission lines, may be utilized in connection with devices incorporating my invention.

What is claimed is:

1. An electron-discharge device comprising: a cathode, an anode, said anode having a plurality of grooves therein and an electron-receiving portion intermediate each pair of adjacent grooves; said grooves constituting primary cavity resonators; a secondary cavity resonator opening into and adapted to be excited from said primary cavity resonators; and means mounted in and shorting some of said primary cavity resonators whereby oscillatory energy from the remaining primary cavity resonators can enter into said secondary cavity resonator at a plurality of selected points spaced along said secondary cavity resonator.

2. An electron-discharge device comprising a cathode, an anode, said anode having a plurality of grooves therein and an electron-receiving portion intermediate each pair of adjacent grooves; said grooves constituting primary cavity resona tors; a toroidal secondary cavity resonator surrounding said anode and opening into and adapted to be excited from said primary cavity resonators; and means mounted in and shorting some of said primary cavity resonators whereby oscillatory energy from the remaining primary cavity resonators can enter into said secondary cavity resonator at a plurality of selected points spaced along said secondary cavity resonator.

3. An electron-discharge device comprising: a cathode; an anode; said anode having an even number of grooves therein and an electron-receiving portion intermediate each pair of adja cent grooves; said grooves constituting primary cavity resonators; a toroidal secondary cavity resonator surrounding said anode and opening into and adapted to be excited from said primary cavity resonators; and means mounted in and shorting some of said primary cavity resonators whereby oscillatory energy from the remaining primary cavity resonators can enter into said secondary cavity resonator at a plurality of selected points spaced along said secondary cavity resonator; said remaining primary cavity resonators being spaced from each other by an odd number of intervening primary cavity resonators.

4. A high-frequency oscillator comprising: an electron-discharge tube having a plurality of primary cavity resonators therein, a secondary cavity resonator opening into and adapted to be excited from said primary cavity resonators, and

means mounted in and shorting some of said. primary cavity resonators, whereby oscillatory' energy from the remaining primary cavity reso-- nators can enter said secondary cavity resonator at a plurality of selected points spaced along said secondary cavity resonator.

5. An electron-discharge device comprising: a cathode; an anode said anode including a block of conducting material provided with a central bore receptive of said cathode; said block including a plurality of slots extending from said central bore to the exterior wall thereof to form a plurality of electron-receiving portions separated by a plurality of primary cavity resonators; a toroidal conducting member connected to said block and having an opening along its inner side closed by said block to form a secondary cavity resonator; said primary cavity resonators opening into said secondary cavity resonator; and means mounted in and closing off certain of said primary cavity resonators to leave only selected ones actually communicating with said secondary cavity resonator.

6. An electron-discharge device comprising: a cathode; an anode; said anode including a block of conducting material provided with a central bore receptive of said cathode; said block including a plurality of slots extending from said central bore to the exterior wall thereof to form a plurality of electron-receiving portions separated by a plurality of primary cavity resonators; a toroidal conducting member connected to said block and having an opening along its inner side closed by said block to form a secondary cavity resonator; said primary cavity resonators opening into said secondary cavity resonator; and conducting plugs mounted in and closing ofi the outer portions of certain of said primary cavity resonators, whereby only selected ones actually communicate with said secondary cavity resonator; 'the length of the unimpeded portion of each of said closed-01f primary cavity resonators being substantially onequarter of the wavelength of the oscillations adapted to be generated by said device, and the length of each of said plugs likewise being substantially one-quarter of said wavelength.

7. An electron-discharge device comprising: a cathode; an anode; said anode including a block of conducting material provided with a central bore receptive of said cathode; said block including a plurality of slots extending from said central bore to the exterior wall thereof to form a plurality of electron-receiving portions separated by a plurality of primary cavity resonators; and a toroidal conducting member connected to said block and having an opening along its inner side closed by said block to form H a secondary cavity resonator; said toroidal conducting member having conducting rings extending from opposite sides of said opening and overlapping opposite sides of said block for a distance equal to substantially one-quarter of the wavelength of the oscillations adapted to be generated in said device; said primary cavity resonators opening into said secondary cavity resonator; said primary cavity resonators each being of a length equal to substantially one-half of said wavelength.

8. An electron-discharge device comprising: a cathode; an anode; said anode including a block of conducting material provided with a central bore receptive of said cathode; said block including a plurality of slots extending from said central bore to the exterior wall thereof to form a plurality of electron-receiving portions separated by a plurality of primary cavity resonators; a toroidal conducting member connected to said block and having an opening along its inner side closed by said block to form a secondary cavity resonator; said primary cavity resonators opening into said secondary cavity resonator; and conducting plugs mounted in and closing oil the outer portions of certain of said primary cavity resonators, whereby only selected ones actually communicate with said secondary cavity resonator; the length of the unimpeded portion of each of said closed-off primary cavity resonators being substantially onequarter of the wavelength of the oscillations adapted to be generated by said device, and the length of each of said plugs likewise being substantially one-quarter of said wavelength; said toroidal conducting member having conducting rings extending from opposite sides of said opening and overlapping opposite sides of said block for a distance equal to substantially onequarter of the wavelength of the oscillations adapted to be generated in said device.

9. An electron-discharge device having a hollow drum-shaped conducting member, a plurality of anode elements of sector-shaped transverse section mounted within said member in spaced relation thereto, whereby the inner wall of said drum-shaped member and the outer surfaces of said sector-shaped anode elements provide a cavity resonator, said anode elements being spaced from each other along radial planes to provide radially-directed slots, the inner ends of said anode elements providing anode segments defining a cathode chamber, a cathode mounted in said chamber, the radial length of said slots being effectively a half-wavelength oi the operating frequency of said device.

10. An apparatus for use at high radio frequencies, including a cavity resonator, means for providing an electron discharge for exciting said resonator, said resonator having an aperture extending through a wall thereof, and a hollow wave guide extending outwlardly from the outside wall of said resonator and opening into the aperture in said resonator, said wave guide comprising an elongated tubular member having its end remote from the apertured wall of said resonator sealed by an insulating medium permeable to electromagnetic Waves, said wave guide having a transverse lip at the outer end thereof for coupling to another wave guide provided with a like lip.

WILLIAM C. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,063,342 Samuel Dec. 8, 1936 2,245,627 Varian June 17, 1941 2,280,824 Hansen et al. Apr. 28, 1942' 2,283,895 Mouromtseff et al. May 19, 1942 2,411,953 Brown Dec. 3, 1946 FOREIGN PATENTS Number Country Date 215,600 Switzerland Nov. 16, 1941 215,602 Switzerland Nov. 1, 1941 

